Liquid crystal display device with light blocking film overlapping drain signal line

ABSTRACT

A liquid crystal display device which can obviate color mixing of colors when a display screen is viewed from oblique directions while enhancing a numerical aperture of a pixel is provided. In a liquid crystal display device having red sub pixels, green sub pixels and blue sub pixels, a width of a light blocking film arranged on a boundary portion between the blue sub pixel and the sub pixel of other color is set larger than a width of a light blocking film arranged on a boundary portion between the red sub pixel and the green sub pixel.

The present application claims priority from Japanese applicationsJP2008-171954 filed on Jul. 1, 2008, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a liquid crystal display device which performs acolor display.

2. Description of the Related Art

In a liquid crystal display device which performs a color display, aunit pixel for color display is constituted of neighboring sub pixels ofthree or more colors.

Each sub pixel includes a colored layer (color filter) corresponding toeach sub pixel, and a viewer can sense a predetermined color due tomixing of lights which pass through the colored layers of the respectivesub pixels.

To realize a monochromatic display, the sub pixels corresponding to thecolor are turned on and, at the same time, the sub pixels correspondingto other colors are turned off.

Further, in performing such a monochromatic display, when a displayscreen is viewed from oblique directions, there arises a drawback(expressed as color mixing in this specification) in which color of thesub pixel in an OFF state which is arranged adjacent to the sub pixel inan ON state and is on a side close to the viewer appears to be mixedwith color of the sub pixel in an ON state. This is because that a paththrough which light passes the sub pixel in an ON state and a paththrough which light passes other sub pixel adjacent to the sub pixel inan ON state exist in a path of light from a backlight, for example.

When substrates which are arranged to face each other in an opposedmanner with liquid crystal sandwiched therebetween are fixed in adisplaced manner in the direction that sub pixels of different colorsare arranged due to irregularities in the manufacture of a liquidcrystal display device, in a monochromatic display, the colored layer ofother sub pixel adjacent to the sub pixel in an ON state approaches aregion of the sub pixel in an ON state or overlaps with the region ofthe sub pixel in an ON state and hence, the drawback on color mixingbecomes particularly conspicuous. This is because that the colored layerof other sub pixel is arranged adjacent to or overlaps with the regionof the sub pixel in an ON state and hence, a width of the path of lightexpands.

Recently, due to the development of a liquid crystal display devicewhich exhibits a so-called excellent wide viewing angle, chances thatthe liquid crystal display device is viewed from oblique directions areincreased and hence, the deterioration of image quality due to theabove-mentioned color mixing becomes more easily recognized.

To cope with such a situation, conventionally, a drawback attributed tothe above-mentioned color mixing is obviated by uniformly increasing awidth of light blocking layers (black matrixes) each of which isarranged between respective sub pixels. That is, the above-mentionedcolor mixing is obviated by blocking light which passes through thecolor filter of other sub pixel adjacent to the sub pixel in an ON stateby the black matrix having a large width.

As documents relating to the present invention, JP-A-11-38426 (patentdocument 1) and JP-A-2005-84097 (patent document 2) are named.

SUMMARY OF THE INVENTION

However, when the width of black matrixes each of which is arrangedbetween the respective sub pixels is uniformly increased as describedabove, a substantial region of a pixel excluding a region for formingthe black matrix is narrowed thus giving rise to a drawback that anumerical aperture of the pixel is lowered.

This drawback lowers brightness of the liquid crystal display device.

It is an object of the present invention to provide a liquid crystaldisplay device which can obviate color mixing of colors of sub pixelswhen a display screen is viewed from oblique directions while enhancinga numerical aperture of a pixel.

In a liquid crystal display device, retardation of liquid crystal is setsuch that efficiency that light which passes through liquid crystal(transmissivity) and a transmissivity ratio (transmission contrastratio) between an ON state and an OFF state is increased. In this case,when retardation of liquid crystal is set such that the transmissivityratio between an ON state and an OFF state is increased, light whichpasses through liquid crystal has property of becoming yellowishcompared with color of the light before the light passes through liquidcrystal.

Accordingly, to prevent the display from becoming yellowish, it may bepossible to adopt a method which uses a light source having bluish colorwhich is a complementary color of yellow.

In a liquid crystal display device which uses such a bluish lightsource, when a panel is viewed from oblique directions in amonochromatic display, color mixing which is generated by mixing bluebecomes more easily visually recognized.

That is, in a red monochromatic display, when the display screen isviewed from oblique directions on a side where the blue pixel isarranged adjacent to the red pixel, color mixing which is caused bymixing blue is emphasized due to a bluish light source and hence, adrawback of color mixing becomes conspicuous. On the other hand, in thered monochromatic display, when the display screen is viewed fromoblique directions on a side where the green pixel is arranged adjacentto the red pixel, a drawback of color mixing generated by mixing greenis hardly visually recognized compared with the drawback of color mixinggenerated by mixing blue.

From such a phenomenon, it is understood that it is necessary toincrease a width of the black matrix between the red pixel and the bluepixel, while it is unnecessary to increase a width of the black matrixbetween the red pixel and the green pixel. Accordingly, compared withthe case in which the width of the black matrixes is uniformlyincreased, a numerical aperture of the pixel can be enhanced.

Also in this case, by arranging the black matrix between the red pixeland the blue pixel toward a center side of the blue pixel in a displacedmanner, it is unnecessary to increase the width of the black matrix.This is because that due to the displacement of the black matrix betweenthe red pixel and the blue pixel toward the center side of the bluepixel, as described above, when the display screen is viewed fromoblique directions on a side where the blue pixel is arranged adjacentto the red pixel in a red monochromatic display, the blue light can beblocked by the black matrix.

The liquid crystal display device of the present invention has thefollowing constitutions, for example.

(1) The present invention is directed to a liquid crystal display deviceincluding: a pair of substrates which is arranged to face each other inan opposed manner with liquid crystal sandwiched therebetween; lightblocking films and color filters which are formed on one substrate outof the pair of substrates; and red sub pixels, green sub pixels, andblue sub pixels which are determined based on colors of the colorfilters, wherein the red sub pixels, the green sub pixels and the bluesub pixels are arranged such that the sub pixels having the same colorare not arranged adjacent to each other in the first direction, thelight blocking film is arranged on a boundary portion between the redsub pixel and the green sub pixel arranged adjacent to each other, on aboundary portion between the green sub pixel and the blue sub pixelarranged adjacent to each other, and on a boundary portion between theblue sub pixel and the red sub pixel arranged adjacent to each other,and a width of the light blocking film arranged on the boundary portionbetween the blue sub pixel and the sub pixel of other color is setlarger than a width of the light blocking film arranged on the boundaryportion between the red sub pixel and the green sub pixel.

(2) In the liquid crystal display device of the present invention havingthe constitution (1), assuming the width of the light blocking filmarranged on the boundary portion between the red sub pixel and the bluesub pixel as Wrb, the width of the light blocking film arranged on theboundary portion between the green sub pixel and the red sub pixel asWgr, and the width of the light blocking film arranged on the boundaryportion between the blue sub pixel and the green sub pixel as Wbg, arelationship of Wrb>Wbg>Wgr is established.

(3) In the liquid crystal display device of the present invention havingthe constitution (1), drain signal lines which supply video signals areformed on another substrate out of the pair of substrates, and the lightblocking film is formed so as to cover the drain signal line as viewedin a plan view.

(4) The present invention is also directed to a liquid crystal displaydevice including: a pair of substrates which is arranged to face eachother in an opposed manner with liquid crystal sandwiched therebetween;light blocking films and color filters which are formed on one substrateout of the pair of substrates; and red sub pixels, green sub pixels, andblue sub pixels which are determined based on colors of the colorfilters, wherein the red sub pixels, the green sub pixels and the bluesub pixels are arranged such that the sub pixels having the same colorare not arranged adjacent to each other in the first direction, thelight blocking film is arranged on a boundary portion between the redsub pixel and the green sub pixel arranged adjacent to each other, on aboundary portion between the green sub pixel and the blue sub pixelarranged adjacent to each other, and on a boundary portion between theblue sub pixel and the red sub pixel arranged adjacent to each other,and assuming a distance between a center line of a width of the lightblocking film arranged on a boundary portion between the red sub pixeland the blue sub pixel arranged adjacent to the red sub pixel and acenter line of a width of the light blocking film arranged on a boundaryportion between the red sub pixel and the green sub pixel arrangedadjacent to the red sub pixel as Lr, and assuming a distance between acenter line of a width of the light blocking film arranged on a boundaryportion between the blue sub pixel and the green sub pixel arrangedadjacent to the blue sub pixel and a center line of a width of the lightblocking film arranged on a boundary portion between the blue sub pixeland the red sub pixel arranged adjacent to the blue sub pixel as Lb, arelationship of Lr>Lb is established.

(5) In the liquid crystal display device of the present invention havingthe constitution (4), assuming a distance between a center line of awidth of the light blocking film arranged on a boundary portion betweenthe green sub pixel and the blue sub pixel arranged adjacent to thegreen sub pixel and a center line of a width of the light blocking filmarranged on a boundary portion between the green sub pixel and the redsub pixel arranged adjacent to the green sub pixel as Lg, a relationshipof Lr>Lg>Lb is established.

(6) In the liquid crystal display device of the present invention havingthe constitution (4), drain signal lines which supply video signals areformed on another substrate out of the pair of substrates, and the lightblocking film is formed so as to cover the drain signal line as viewedin a plan view.

Here, the above-mentioned constitutions constitute merely one example ofthe present invention, and the present invention can be suitablymodified without departing from the gist of the technical concept of thepresent invention. Further, constitutional examples of the presentinvention other than the above-mentioned constitutions will becomeapparent from the description of the whole specification or drawingswhich explain the present application.

The liquid crystal display device having such a constitution can obviatecolor mixing of colors when a display screen is viewed from obliquedirections while enhancing a numerical aperture of a pixel.

Other advantageous effects obtained by the present invention will becomeapparent from the description of the whole specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing one embodiment of a liquid crystal displaydevice of the present invention;

FIG. 2 is an equivalent circuit diagram in a pixel of the liquid crystaldisplay device of the present invention;

FIG. 3 is a cross-sectional view taken along a line III-III in FIG. 1;and

FIG. 4 is a plan view showing another embodiment of a liquid crystaldisplay device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention are explained in conjunction withdrawings. Here, in all embodiments and all drawings used for explainingthe present invention, identical or similar constitutional parts aregiven same symbols and their repeated explanation is omitted.

Embodiment 1 Equivalent Circuit of Pixel

FIG. 2 shows an equivalent circuit of a so-called IPS (In PlaneSwitching)-type liquid crystal display device. Although FIG. 2 shows theequivalent circuit, the equivalent circuit corresponds to an actualliquid crystal display device geometrically.

As shown in FIG. 2, the liquid crystal display device includes gatesignal lines GL which extend in the x direction and are arrangedparallel to each other in the y direction in the drawing and drainsignal lines DL which extend in the y direction and are arrangedparallel to each other in the x direction in the drawing. A regionsurrounded by a pair of neighboring gate signal lines GL and a pair ofneighboring drain signal lines DL constitutes a pixel region. Here, amass of the pixel regions constitutes a display region.

The pixel region includes a thin film transistor TFT which constitutes aswitching element, and the thin film transistor TFT is turned on inresponse to a signal (scanning signal) from the gate signal line GL.

Further, the pixel region includes a pixel electrode PX, and a signal(video signal) is supplied to the pixel electrode PX from the drainsignal line DL via the thin film transistor TFT. Further, the pixelregion includes a counter electrode CT, and a reference signal whichbecomes the reference with respect to the video signal is supplied tothe counter electrode CT via a counter voltage signal line CL.

An electric field is generated between the pixel electrode PX and thecounter electrode CT by supplying the video signal to the pixelelectrode PX, and molecules of liquid crystal in the pixel region areactivated by the electric field.

In the liquid crystal display device having such a constitution, inresponse to the sequential supply of a scanning signal to the respectivegate signal lines GL, a pixel row in which the pixels are arrangedparallel to each other in the x direction in the drawing is selected.Here, in response to the supply of a predetermined video signal to eachdrain signal line DL, the respective pixels in the pixel row are driventhus allowing the display region to display an image.

(Constitution of Pixel)

FIG. 1 is a constitutional view showing one embodiment of the liquidcrystal display device of the present invention, and is a plan viewshowing the constitution of a liquid-crystal-side surface of a pair ofsubstrates which is arranged to face each other in an opposed mannerwith liquid crystal sandwiched therebetween.

That is, FIG. 1 shows a TFT substrate TBS on which parts whichconstitute the equivalent circuit shown in FIG. 2 are formed, and acounter substrate FBS which is arranged to face the TFT substrate TBS inan opposed manner with the liquid crystal sandwiched therebetween. FIG.1 is also a plan view of the liquid crystal display device as viewedfrom a counter substrate side in a see-through manner. Here, FIG. 3 is across-sectional view taken along a line III-III in FIG. 1.

The TFT substrate TBS is constituted as follows. First of all, the TFTsubstrate TBS includes a substrate SUB1 (see FIG. 3) made of glass, forexample, and a background films GDL1, GDL2 (see FIG. 3) are formed on aliquid-crystal-LC-side surface of the substrate SUB1. The backgroundfilms GDL1, GDL2 prevent impurities in the inside of the substrate SUB1from entering into semiconductor layers of the thin film transistors TFTdescribed later.

A semiconductor layer PS made of poly-silicon (p-Si), for example, isformed in a region of an upper surface of the background film GDL2 wherethe thin film transistor TFT is formed for every pixel region, and aninsulation film GI (see FIG. 3) is formed so as to cover thesemiconductor layer PS. The insulation film GI functions as a gateinsulation film in the region where the thin film transistor TFT isformed.

On an upper surface of the insulation film GI, the gate signal lines GLare formed such that the gate signal lines GL extend in the x directionand are arranged parallel to each other in the y direction in thedrawing. Here, the gate signal line GL is formed so as to intersect acenter portion of the semiconductor layer PS, and forms a gate electrodeof the thin film transistor TFT at an intersecting portion.

Further, on an upper surface of the insulation film GI, an interlayerinsulation film IN1 is formed in a state that the interlayer insulationfilm IN1 also covers the gate signal lines GL, and on an upper surfaceof the interlayer insulation film IN1, the drain signal lines DL areformed in a state that the drain signal lines DL extend in the ydirection and are arranged parallel to each other in the x direction inthe drawing. The drain signal line DL is electrically connected with oneend of the semiconductor layer PS via a through hole which is formed inthe interlayer insulation film IN1. A connection portion of the drainsignal line DL which is connected with the semiconductor layer PSfunctions as a drain electrode DT of the thin film transistor TFT.

On an upper surface of the interlayer insulation film IN1, sourceelectrodes ST of the thin film transistors TFT are formed, and eachsource electrode ST is electrically connected with another end of thesemiconductor layer PS via a through hole which is formed in theinterlayer insulation film IN1. The source electrode ST is electricallyconnected with a pixel electrode PX described layer.

On an upper surface of the interlayer insulation film IN1, asequentially stacked body constituted of a protective film PAS1 and aprotective film PAS2 (see FIG. 3) is formed so as to also cover the thinfilm transistors TFT. The sequentially stacked body is provided forpreventing the thin film transistors TFT from directly coming intocontact with the liquid crystal LC. The protective film PAS1 is formedof an organic insulation film, and the protective film PAS2 is formed ofan organic insulation film. The reason that the protective film PAS2 isformed of the organic insulation film is that the protective film PAS2can be formed by coating so that a surface of the sequentially stackedbody can be leveled.

On an upper surface of the protective film PAS2, counter electrodes CT(see FIG. 3) which are formed of a transparent conductive layer made ofITO (Indium Tin Oxide), for example, are formed. The counter electrodeCT is formed of a surface electrode which extends over the neighboringpixel region, and also functions as a voltage counter signal line CLshown in FIG. 2. A hole (indicated by symbol HL in FIG. 1) is formed ina portion of the counter electrode CT which overlaps with the sourceelectrode ST of the thin film transistor TFT. The hole is provided foravoiding electrical short-circuiting between the counter electrode CTand the pixel electrode PX when the pixel electrode PX described laterand the source electrode ST are connected with each other via thethrough hole TH.

An interlayer insulation film IN2 is formed on an upper surface of thecounter electrodes CT, and the pixel electrodes PX are formed on anupper surface of the interlayer insulation film IN2 at respective pixelregions. The pixel electrode PX is constituted of a transparentconductive layer made of ITO (Indium Tin Oxide), for example. Further,the pixel electrode PX includes a plurality of (for example, two) linearelectrode portions which extends in the y direction and is arrangedparallel to each other in the x direction in the drawing, and theselinear electrode portions have thin-film-transistor-TFT-side endportions thereof electrically connected with each other.

Further, the pixel electrode PX is electrically connected with thesource electrode ST of the thin film transistor TFT via the through holeTH formed in the interlayer insulation film IN2, the protective filmPAS2 and the protective film PAS1 in a region where the plurality oflinear electrode portions of the pixel electrode PX is connected witheach other.

On an upper surface of the interlayer insulation film IN2 on which thepixel electrode PX is formed, an alignment film ORI1 is formed so as toalso cover the pixel electrodes PX. The alignment film ORI1 decides theinitial alignment direction of molecules of liquid crystal.

The counter substrate FBS which is arranged to face the above-mentionedTFT substrate TBS with the liquid crystal LC sandwiched therebetween isconstituted as follows. First of all, the counter substrate FBS includesa substrate SUB2 (see FIG. 3) made of glass, for example, and blackmatrixes BM (light blocking films) are formed on aliquid-crystal-LC-side surface of the substrate SUB2.

For example, in this embodiment, the black matrixes BM are formed so asto cover the drain signal lines DL which are formed on theTFT-substrate-TBS side. Further, with respect to the respective blackmatrixes BM which are arranged parallel to each other in the x directionin the drawing, three neighboring black matrixes BM have differentwidths respectively, and the same width pattern is repeated for everythree black matrixes BM in the x direction in the drawing. The widths ofthese black matrixes BM are explained in detail later.

Further, color filters are provided in such a manner that each colorfilter is formed between the neighboring black matrixes BM. These colorfilters FL are arranged in the x direction in the drawing in order ofthe green color filter FL(G), the red color filter FL(R), the blue colorfilter FL(B), the green color filter FL(G), the red color filter FL(R),. . . , for example. Regions which are covered with the red colorfilters FL(R) constitute red sub pixels PX(R), regions which are coveredwith the blue color filters FL(B) constitute blue sub pixels PX(B), andregions which are covered with the green color filters FL(G) constitutegreen sub pixels PX(G), and these sub pixels are arranged adjacent toeach other in the x direction in the drawing. These three sub pixelshaving different colors constitute a unit pixel for color display.

An overcoat film OC which is formed of a resin film, for example, isformed on upper surfaces of these color filters, and a surface of theovercoat film OC is leveled. Further, an alignment film ORI2 is formedon an upper surface of the overcoat film OC, and the alignment film ORI2decides the initial alignment direction of molecules of the liquidcrystal LC.

Although not shown in the drawing, on a surface of the substrate SUB1 ona side opposite to the substrate SUB2, a backlight having a light sourceis arranged. When the retardation of the liquid crystal LC is set suchthat a transmissivity contrast ratio of the pixel is increased, lightwhich passes through the liquid crystal becomes yellowish and hence, itis preferable to use a bluish light source which is a complementarycolor of yellow.

Here, the widths of the above-mentioned black matrixes BM are explained.Assuming the width of the black matrix BM arranged between the red subpixel PX(R) and the blue sub pixel PX(B) as Wrb, assuming the width ofthe black matrix BM arranged between the green sub pixel PX(G) and thered sub pixel PX(R) as Wgr, and assuming the width of the black matrixBM arranged between the blue sub pixel PX(B) and the green sub pixelPX(G) as Wbg, a relationship of Wrb≠Wgr≠Wbg and a relationship ofWrb>Wbg>Wgr are established.

In the liquid crystal display device having the above-mentionedconstitution, in a monochromatic display of the red sub pixel PX(R),when the display screen is viewed from oblique directions on a sidewhere the blue sub pixel PX(B) is arranged adjacent to the red sub pixelPX(R), a drawback of color mixing which is generated by mixing blue isemphasized due to a bluish light source and becomes conspicuous.Accordingly, it is necessary to block light to which blue is mixed usingthe black matrix BM arranged between the red sub pixel PX(R) and theblue sub pixel PX(B). In this case, the increase of the width Wrb of theblack matrix BM becomes inevitable.

On the other hand, in the red monochromatic display, when the displayscreen is viewed from oblique directions on a side where the green subpixel PX(G) is arranged adjacent to the red sub pixel PX(R), a drawbackof color mixing which is generated by mixing green is hardly viewedcompared with the drawback of color mixing generated by mixing blue.

Further, it is confirmed that, a degree of viewing of color mixing inthe observation of the display screen from oblique directions on a sidewhere the blue sub pixel PX(B) is arranged adjacent to the green subpixel PX(G) in a green monochromatic display is smaller than a degree ofcolor mixing of blue in the monochromatic display of the red sub pixelPX(R) and is larger than a degree of color mixing of green in themonochromatic display of the red sub pixel PX(R). Accordingly, assumingthe width of the black matrix BM arranged between the blue sub pixel andthe green sub pixel as Wbg, the width Wbg can be set so as to satisfythe relationship of Wrb>Wbg>Wgr.

As has been explained heretofore, the liquid crystal display device ofthis embodiment can enhance a numerical aperture of each pixel comparedwith a case where widths of the black matrixes BM are uniformlyincreased.

Embodiment 2

FIG. 4 is a constitutional view showing another embodiment of the liquidcrystal display device according to the present invention, and FIG. 4corresponds to FIG. 1.

In FIG. 4, to compare the constitution of this embodiment with theconstitution shown in FIG. 1, first of all, a width of the black matrixBM arranged between the green sub pixel PX(G) and the red sub pixelPX(R), a width of the black matrix BM arranged between the red sub pixelPX(R) and the blue sub pixel PX(B), and a width of the black matrix BMarranged between the blue sub pixel PX(B) and the green sub pixel PX(G)are set equal. The widths of the respective black matrixes BM can be setto values which fall within a range allowable from a viewpoint of anumerical aperture of the sub pixel.

The black matrix BM arranged between the red sub pixel PX(R) and theblue sub pixel PX(B) is formed in a slightly displaced manner toward ablue sub pixel PX(B) side with respect to the drain signal line DL whichis covered with this black matrix BM. Due to such formation of the blackmatrix BM, in a monochromatic display of the red sub pixel PX(R), when adisplay screen is viewed from oblique directions on a side where theblue sub pixel PX(B) is arranged adjacent to the red sub pixel PX(R),mixing of blue light can be blocked by the black matrix BM which isarranged in a displaced manner toward the blue sub pixel PX(B) side. Inthis embodiment, the respective drain signal lines are arranged at equalinterval in the direction that the respective drain signal lines arearranged parallel to each other.

On the other hand, the black matrix BM arranged between the green subpixel PX(G) and the blue sub pixel PX(B) and the black matrix BMarranged between the green sub pixel PX(G) and the red sub pixel PX(R)are formed with no displacement with respect to the drain signal linesDL which are covered with these black matrixes BM, and the center linesof the black matrixes BM and the drain signal lines DL are substantiallyaligned with each other. In a monochromatic display of the green subpixel PX(G), even when blue is mixed in the observation of the displayscreen from oblique directions on a side where the blue sub pixel PX(B)is arranged adjacent to the green sub pixel PX(G), color mixing ishardly visually recognized so that the black matrix BM between the greensub pixel PX(G) and the blue sub pixel PX(B) can be formed in a usualform.

Due to such constitution, according to this embodiment, assuming adistance between the center of the black matrix BM arranged between thered sub pixel PX(R) and the blue sub pixel PX(B) arranged adjacent tothe red sub pixel PX(R) and the center of the black matrix BM arrangedbetween the red sub pixel PX(R) and the green sub pixel PX(G) arrangedadjacent to the red sub pixel PX(R) as Lr, assuming a distance betweenthe center of the black matrix BM arranged between the blue sub pixelPX(B) and the green sub pixel PX(G) arranged adjacent to the blue subpixel PX(B) and the center of the black matrix BM arranged between theblue sub pixel PX(B) and the red sub pixel PX(R) arranged adjacent tothe blue sub pixel PX(B) as Lb, and assuming a distance between thecenter of the black matrix BM arranged between the green sub pixel PX(G)and the blue sub pixel PX(B) arranged adjacent to the green sub pixelPX(G) and the center of the black matrix BM arranged between the greensub pixel PX(G) and the red sub pixel PX(R) arranged adjacent to thegreen sub pixel PX(G) as Lg, a relationship of Lr>Lg>Lb is established.

The liquid crystal display device having such a constitution can, inobviating color mixing of colors when the display screen is viewed fromoblique directions, set the widths of the respective black matrixes tominimum values thus enhancing a numerical aperture of the pixels.

Although the embodiments have been explained in conjunction with theexample in which the liquid crystal display device is an IPS-type liquidcrystal display device, it is needless to say that the technique of thepresent invention is not limited to the IPS-type liquid crystal displaydevice. That is, by applying the technique of the present invention to aVA (vertical alignment) type liquid crystal display device or a TN(twisted nematic) type liquid crystal display device, it is possible toavoid color mixing and, at the same time, to enhance a numericalaperture.

1. A liquid crystal display device comprising: a pair of substrateswhich is arranged to face each other in an opposed manner with liquidcrystal sandwiched therebetween; light blocking films and color filtersformed on one substrate of the pair of substrates; red sub pixels, greensub pixels, and blue sub pixels determined based on colors of the colorfilters; and drain signal lines, thin film transistors, and pixelelectrodes formed on an other substrate of the pair of substrates;wherein drain electrodes of the thin film transistors are connected tothe drain signal lines, and the pixel electrodes are connected to thethin film transistors; wherein the red sub pixels, the green sub pixelsand the blue sub pixels are arranged in a first direction; wherein thelight blocking films are overlapped with the drain signal lines, andarranged on a boundary portion between the red sub pixel and the greensub pixel arranged adjacent to each other, on a boundary portion betweenthe green sub pixel and the blue sub pixel arranged adjacent to eachother, and on a boundary portion between the blue sub pixel and the redsub pixel arranged adjacent to each other; and wherein a width of thelight blocking film arranged on the boundary portion between the bluesub pixel and the sub pixel of a color other than a blue color anddisposed between the pixel electrodes in the first direction is setlarger than a width of the light blocking film arranged on the boundaryportion between the red sub pixel and the green sub pixel and disposedbetween the pixel electrodes in the first direction.
 2. A liquid crystaldisplay device according to claim 1, wherein assuming the width of thelight blocking film arranged on the boundary portion between the red subpixel and the blue sub pixel as Wrb, the width of the light blockingfilm arranged on the boundary portion between the green sub pixel andthe red sub pixel as Wgr, and the width of the light blocking filmarranged on the boundary portion between the blue sub pixel and thegreen sub pixel as Wbg, a relationship of Wrb>Wbg>Wgr is established. 3.A liquid crystal display device according to claim 1, wherein the lightblocking films are overlapped with the drain electrodes, and the widthof the light blocking film arranged on the boundary portion between theblue sub pixel and the sub pixel of the color other than the blue colorand overlapped with the drain electrode is set larger than a width ofthe light blocking film arranged on the boundary portion between the redsub pixel and the green sub pixel and overlapped with the drainelectrode.
 4. A liquid crystal display device comprising: a pair ofsubstrates which is arranged to face each other in an opposed mannerwith liquid crystal sandwiched therebetween; light blocking films andcolor filters formed on one substrate of the pair of substrates; red subpixels, green sub pixels, and blue sub pixels determined based on colorsof the color filters, drain signal lines, thin film transistors, andpixel electrodes formed on an other substrate of the pair of substrates;wherein drain electrodes of the thin film transistors are connected tothe drain signal lines, and the pixel electrodes are connected to thethin film transistors; wherein the red sub pixels, the green sub pixelsand the blue sub pixels are arranged in a first direction, wherein thelight blocking films are overlapped with the drain signal lines, andarranged on a boundary portion between the red sub pixel and the greensub pixel arranged adjacent to each other, on a boundary portion betweenthe green sub pixel and the blue sub pixel arranged adjacent to eachother, and on a boundary portion between the blue sub pixel and the redsub pixel arranged adjacent to each other; and wherein the drain signallines are arranged at equal interval in the first direction, and whereina distance Lr between a center line of a width of the light blockingfilm arranged on the boundary portion between the red sub pixel and theblue sub pixel and a center line of a width of the light blocking filmarranged on the boundary portion between the red sub pixel and the greensub pixel is larger than a distance Lb between a center line of a widthof the light blocking film arranged on the boundary portion between theblue sub pixel and the green sub pixel and a center line of the width ofthe light blocking film arranged on the boundary portion between theblue sub pixel and the red sub pixel.
 5. A liquid crystal display deviceaccording to claim 4, wherein a distance Lb between the center line ofthe width of the light blocking film arranged on the boundary portionbetween the green sub pixel and the blue sub pixel and the center lineof the width of the light blocking film arranged on the boundary portionbetween the green sub pixel and the red sub pixel as Lg, is larger thanLb and smaller than Lr.
 6. A liquid crystal display device according toclaim 1, wherein the drain signal lines extend in a second directiontransverse to the first direction, the light blocking films arranged onthe boundary portions extend in the second direction between the subpixels of different colors and have substantially a same width over theextent of the boundary portions between the sub pixels of the differentcolors.
 7. A liquid crystal display device according to claim 2, whereinthe drain signal lines extend in a second direction transverse to thefirst direction, the light blocking films arranged on the boundaryportions extend in the second direction between the sub pixels ofdifferent colors have substantially a same width over the extent of theboundary portions between the sub pixels of the different colors.
 8. Aliquid crystal display device according to claim 3, wherein the drainsignal lines extend in a second direction transverse to the firstdirection, the light blocking films arranged on the boundary portionsextend in the second direction between the sub pixels of differentcolors have substantially a same width over the extent of the boundaryportions between the sub pixels of the different colors.
 9. A liquidcrystal display device according to claim 4, wherein the drain signallines extend in a second direction transverse to the first direction,the light blocking films arranged on the boundary portions extend in thesecond direction between the sub pixels of different colors havesubstantially a same width over the extent of the boundary portionsbetween the sub pixels of the different colors.